This invention relates to a robot arm for use in transporting or manipulating a semiconductor wafer from one station to another one within a processing apparatus for manufacturing a semiconductor device.
A robot arm of the type described has been proposed in Abbe U.S. Pat. No. 4,897,015 and is suitable for manipulating semiconductor wafers. The robot arm comprises an end effector at an end of the robot arm and is operable to convert rotary motion into radial or linear motion of the end effector by driving a single motor. Such conversion of the rotary motion into the radial motion is established by selecting rotation ratios between the end effector and the first arm unit and between the first arm unit and the second arm unit and also by selecting lengths of the first and the second arm units.
In addition, the robot arm proposed by Abbe enables rotation motion and elevation motion depicted at .theta. and Z, respectively. To this end, the end effector is pivotally connected to the first arm unit which is in turn pivotally jointed to a second arm unit which defines a reference point. The radial motion of the end effector is carried out under control of the single motor while auxiliary motor drives are also prepared to carry out the rotation and the elevation motions.
However, no disclosure is made in Abbe at all about a practical mechanism for establishing the rotation motion and the elevation motion, because the auxiliary motor drives are illustrated in blocks in Abbe. Accordingly, it is difficult to anticipate the practical mechanism for the rotation and the elevation motions from Abbe.